122 CLINICAL BACTERIOLOGY AND HiEMATOLOGY 



(other than those which are dictated by the interests of the 

 patient) are necessary. But in the greater proportion of cases 

 this is not enough, and cultures must be obtained. To this end 

 it is absolutely essential that the most scrupulous precautions should 

 be taken against contamination of the fluid by the organisms 

 which are constantly present in the air and in the skin, or the 

 results will be worthless. The precautions taken must be as 

 complete as those which are used before an operation upon a 

 joint. Indeed, a fresh precaution has to be taken, for whereas 

 the presence in the skin of a small quantity of an antiseptic 

 would not be detrimental to a surgical operation, it might, by 

 getting into the fluid, nullify a bacteriological examination. 

 Hence the skin must be aseptic, and free from any antiseptic 

 chemical. 



The technique, as far as aseptic precautions are concerned, is 

 as follows : The skin at the region to be punctured is first 

 thoroughly cleaned with soap, hot water, and (if the patient can 

 stand it) a nail-brush. Then layer after layer of some reliable 

 antiseptic lotion is painted on, each layer being allowed to soak 

 in before the next is applied. The most suitable lotions for the 

 purpose are perchloride of mercury (i in i,ooo), biniodide 

 of mercury (i in 500 of methylated spirit), or carbolic acid 

 (i in 20). 



After being allowed to act for at least ten minutes, the skin is 

 to be thoroughly cleansed with methylated spirit ; this should be 

 rubbed in with a piece of cotton-wool, and should be poured 

 copiously over the area. The operation may now proceed. 



Where possible it is preferable to apply a dressing of lint 

 soaked in one of the above lotions (which need be of only half 

 the strength) for a few hours. 



The puncture may be made by using some sort of exploring 

 syringe, or a hollow needle without any means for aspiration. 

 The former is used for the removal of fluid from the pleura 

 or synovial cavity, the latter in performing lumbar puncture. 

 But it is necessary that the whole of the instrument used should 

 be rendered sterile by heat ; chemical antiseptics are as a rule 

 inadmissible. In the case of a hollow needle no difficulty occurs ; 

 some hypodermic syringes, however, will not stand boiling, and 

 these are useless for the purpose, as the apparatus which is to 

 be used must be boiled for at least five minutes. 



We shall now deal with the most important cavities of the 



